Method for cracking petroleum oils



jan, 1l, W38. v'n1 KENNEY 105,393

METHOD FOR CRAOKING PETROLEUM OILS l Filed oct. 21, 1935 Patented Jan.11, 1938 e ne UNITEDy STATES PATENT crece METHOD Foa cRAoKING PETROLEUMons Thomas Kenney, Robinson, Ill., assigner of onefourth to Sylvia S.Lee, Kenilworth, Ill., and one-fourth to Ira J. Wilson, Winnetka, Ill.

Application October 21, 1935, Serial No. 45,942 v2 claims. (c1. 19e-ss)rI'his invention relates to the cracking of petroleum oil and aimsprimarily to obtain from the crude oil a very much higher percentage ofcracked product than has heretofore been obtained, and to attain thisresult at a lower cost per unit of volume by employing apparatus whichcan be installed and operated moreeconomically than that heretoforeused, and which will obviate the frequent shut-downs heretofore requiredfor cleaning purposes, and will also eliminate the difculties heretoforeencountered as the result of the formation of coke or carbon deposits inthe apparatus heretofore employed.

In the commercial cracking methods now commonly employed the crude oilis first run through a still which drives oi about to 80% of theadmitted oil, the remainder being left as a viscous heavy tar which isdrawn off without vaporizing. A small amount of cracking is done in thisstill and the cracked products are segregated as far as possible whilethe remainder, consisting of over fty percent of the crude oil admittedto the still, is condensed and sent through a cracking still where it isheated to cracking temperature. The cracked product from this still issegregated while the remainder is circulated around and again passedthrough the still, this process of recirculation being continued fromfour to six times, each passage throughthe still resulting in thecracking of from 10 to 15% of theproduct circulated into the still whileto 90% comes out of the cracking still in practically the same conditionthat it entered.

This repeated recirculation through the still makes the process veryexpensive not only because of the repeated heating and cooling off ofthe noncracked oils being circulated, but also because of the timeconsumption required in carrying out the process. Furthermore, thoseportions of the oils in immediate contact with the inner surfaces of thecoils in the stills where the oil is heated become overheated to a pointof carbonization, with the result that carbon or coke accumulates sorapidly on the inner surfaces of the coils that frequent shutdowns ofthe still are necessary for the purpose of cleaning out the accumulatedcoke and carbon or replacing the clogged coils with new ones. Thenecessarily frequent shutting down and cooling olf of the plant and thecleaning or replacement of the coils are a large item of expense in theoperation of these stills which adds materially to the cost ofproduction of the cracked product.

In accordance with my present invention the heretofore frequentshut-downs of the plant and the expense of cleaning and replacingclogged still coils are entirely'eliminated, and, in fact, theproduction of coke and carbon which causes these shut-downs is itselfobviated by my method of cracking.

My invention contemplates the passageV of the product to be rened onlyonce through a still in which the product is brought to a crackingtemperature without heating any portion of lit to a point which willresult in carbonization or coke production. Consequently the productionof coke or carbon is obviated and the total constituents of the crudeoil are subject to cracking and, in fact, will be practically allcracked, so that the-quam tity of residuum left will be practicallynegligible, consisting of only a very small fraction of the amount leftin the rst heating still of the present commercial apparatus abovedescribed.

These results are obtained in accordance with my invention by entirelyeliminating the furnace and all combustion or direct heatingapparatuswhich have heretofore been considered necessary forheating theoil. The elimination of the high temperature in the still whichinevitably produced coking and carbonization obviously does awaywiththese detrimental factors. The cracking temperatures areproduced with myinvention by a prolonged mechanical agitation of the still contents sothat the entire contents are thoroughly and homogeneously mixed anduniformly raised in temperature under a predetermined pressure until thedesired cracking temperature is reached, whereupon a portion of thecracked contents are removed and segregated and at the same time thestill is replenished with crude oil to maintain the requisite stillpressure. This method enables a practically continuous operation duringwhich the still contents are being practically continuously heated,drawn oiI", and replenished.

To facilitate an understanding of my invention I have shown ratherdiagrammatically on the accompanying drawing a preferred form ofapparatus by which my improved method may be practiced.

Referring to the drawing:

Fig. 1 represents diagrammatically the apparatus contemplated by myinvention; and

Fig. 2 is an enlarged sectional View through the still taken on the line2 2.

Referring to the drawing more speciiically, reference character 3indicates a petroleum oil storage tank from which the crude oil isdelivered by a pump l through a pipe 5 to the tower 6 at a point belowthe oil level therein indicated by l. A discharge pipe 8 leading fromthe bottom of the tower to a sump is equipped with an. emergency reliefvalve 9.

Enroute to the tower the crude oil'pipe '5 passes throughout a portionof its length through the vapor line l! leading from the top of thetower and through which the cracked product is discharged to the usualcondenser. The length of piping in which the oil pipe is dispcsed withinthe vapor line serves asia heat exchanger in which heat units aretransferred from the hot issuing vapors to the incoming crude oil, whichin normal operation will raise the temperature of this crude oil to 400or more degrees Fahrenheit.

From the lower portion of the tower the crude oil is withdrawn through apipe I2 by a pressure pump I3 from which it is discharged througha lineI4 into the still I5, which comprises a closed container of suitableshape and size adapted to contain the oil under a pressure ofapproximately 200 pounds, at which it is delivered by the pump I3. Apressure relief valve i6 adapted to open under excessive pressure, ifsuch be generated in the still, may be connected at any suitable pointto the still, but in this instance is illustrated as being located inthe pipe I4 and equipped with a discharge pipe I1 leading to a sump, orelsewhere, through which excess'pressure may be discharged. A checkvalve I8 interposed in the pipe I4 prevents reverse flow toward thepump.

The pump I3 may be driven in any suitable manner, but is hereillustrated as driven by an electric motor I9 which is started andstopped by a pressure actuated'controller 2| connected through suitablepiping 22 with the still, so that the pump is operated just suflicientlyto maintain the predetermined desired pressure'in the still.

The still is preferably equipped with the usual manhole 23 through whichaccess to the interior of the still may be obtained, with a drain pipe24 having a manually operable valve 25, with a pressure gauge 26 and athermometer 21. The still also, as will be observed from Fig. 2, isenclosed in a heavy insulated jacket 28 to prevent heat losses from thestill.

Instead of heating the still contents by the application of heat to theexterior of the still as has heretofore been customary, the contents, inaccordance with my invention, are heated by mechanical agitation. Forthis purpose one or more agitators 29 are disposed within the still andmounted upon a shaft 3l projecting through one end of the still andsealed against leakage around the shaft by a packing gland 32. Endthrust of the shaft is absorbed by a suitable bearing 33, preferably ofroller or ball bearing type. A power shaft 34 connected with or forminga continuation of shaft 3| is driven by a prime mover 35, which may be aDiesel engine, a gasoline motor, or other economical power unit.

A discharge pipe 36 leading from the top of the still is adapted todeliver into thc tower discharge through this pipe being controlled by athermostatically controlled valve 31, the thermo element 3B of whichprojects into the still, as shown. The tower may also be provided with athermostat 39 and a pressure indicator 4I, if desired.

In accordance with my invention the crude oil is pumped from the storagetank 3 through the heat exchanger in which it is heated to 400 or moredegrees, thence into the lower portion of the tower from which it isdelivered by the pressure controlled pump I3 into the still I5 atapproximately 200 pounds or other desired pressure, which pressure ismaintained through the pressure pump control device 2|. Within the stillthe oil under pressure is subjected to agitacharge valve 31 is set. Whenthis temperature is reached the valve 31 automatically opens, permittingdischarge of cracked products into the tower, fromwhence they aredischarged through the vapor line II to the usual condenser. Since thepressure in the still is relieved by the opening of the valve 31 and thedischarge of a portion of the cracked products, the still is replenishedwith crude oil by the starting of the pump I3 which continues to operateuntil the predetermined pressure in the still has been restored. Theoperation of the valve 31 and the pump I3 may be intermittent, but'whenthe apparatus has been operating for some time the valve 31 will usuallystand in a substantially uniform partially open position and the pump I3will operate practically continuously, thereby enabling the cracking tobe performed in a substantially continuous operation.

Since there is no application of flame to the still and the stillcontents are never subjected to a temperature in excess of the desiredcracking temperature, the production of coke and carbonized solids isobviated and practically all of the crude oil delivered to the still iseventually cracked and segregated as a cracked product.

Obviously the details disclosed may be varied within considerablelimits, as may the steps of my improved method, without departing fromthe essence of the invention as defined in the following claims.

I claim:

1. A hydrocarbon oil conversion process which comprises introducing theoil at below cracking temperature into an unheated reaction zone,subjecting the oil in said zone to thorough and homogeneous mechanicalagitation to raise the temperature of the oil, maintaining the oil undersuperatmospheric pressure during such agitation and continuing theagitation until the oil has attained a cracking temperature and substanwtial cracking thereof has been effected, the oil in said zone beingraised to cracking temperature and cracked solely by the heat generatedby said mechanical agitation, and removing resultant cracked productsfrom said Zone.

' 2. A hydrocarbon oil conversion process which comprises introducingthe oil at below cracking temperature into an unheated reaction zone,subjecting the oil in said zone to thorough and homo-- geneousmechanical agitation to raise the temi' perature of the oil, maintainingthe oil under superatmospherc pressure during such agitation andcontinuing the agitation until the oil has attained a crackingtemperature and substantial cracking thereof has been effected, the oilin said zone being raised to cracking temperature and cracked solely bythe heat generated by said mechanical agitation, releasing resultantcracked products from the reaction zone in response to a predeterminedcracking temperature in said zone, and replenishing the reaction zonewith fresh charging oil in response to pressure drop in said zoneresulting from the release of said cracked products.

THOMAS KENNEY.

